This invention relates generally to the control of liquid surface levels or levels in systems that include more than one liquid body; and more specifically concerns the control of liquid surface level in one liquid body to and from which liquid is circulated via lines circulating liquid between a second liquid body and a pump. Typically, such liquid bodies are represented by a relatively small size spa (or waterfall or fountain) and a relatively large size swimming pool.
The water in swimming pools is normally circulated to and from a filter, as via a pump. Recently, spas have come into popular use, and are connected into the pool water circulation system. Such spas are commonly located at a higher level than the pool, and have had to be placed close to the pool so overflow water would fall into or drain into the pool. No way was known, prior to the present invention, to control common circulation in such manner that the spa (or fountain, waterfall or other device) could be located away from the pool, and so that overflow would not occur, and at the same time the water level in the spa could be kept at a different level from that in the pool; more specifically, the simple, efficient structure; mode of operation and results of the present invention were not therefore known.